4. Debugging
The Thunderboard EFM8UB3 contains an on-board fully functional SEGGER J-Link Debugger that interfaces to the target EFM8 using
the Silicon Labs 2-Wire (C2) debug interface. The debugger allows the user to download code and debug applications running in the
target EFM8. Additionally, it also provides a virtual COM port (VCOM) to the host computer that is directly connected to the target devi-
ce's serial port, for general purpose communication between the running application and the host computer.
An external Silicon Labs debugger can also be used with the board by connecting it to the Mini Simplicity connector. This allows ad-
vanced debugging features as described in section
4.3 Mini Simplicity Connector
. A Silicon Labs Starter Kit (STK) is a good example of
a debugger that can be used with the Thunderboard EFM8UB3 when connected through a debug adapter.
Note:
When using an external debugger, the "Power Source" slide switch must be placed in the "DBG USB" position, and the debug
USB cable must be removed to ensure correct operation.
Figure 4.1 Thunderboard EFM8UB3 Debugging Possibilities on page 13
shows the possible debug options.
Figure 4.1. Thunderboard EFM8UB3 Debugging Possibilities
4.1 On-board Debugger Considerations
The on-board debugger is a SEGGER J-Link debugger running on an EFM32 Giant Gecko. The debugger is connected to the C2 and
VCOM pins of the target EFM8 through a level shift and isolation circuit. When the debug USB cable is inserted, the on-board debugger
is automatically active and takes control of the C2 and VCOM interfaces. This means that serial wire debug and communication will
not
work with an external STK connected through the Mini Simplicity connector at the same time.
When the debug USB cable is connected, the target EFM8 voltage domain (VMCU) is used to power parts of the level shift and isola-
tion circuit. Furthermore, depending on the "Power Source" slide switch position, the debugger itself may also be powered from the
VMCU rail. These considerations should be taken into account when trying to measure the EFM8 current consumption on the kit while
using the on-board debugger.
When the debug USB cable is disconnected, the on-board debugger is powered down and the level shift and isolation circuit is put in a
partially powered down state, minimizing both leakage current and quiescent current from the target EFM8 voltage domain (VMCU).
This means that high performance power measurements of the EFM8 with either Advanced Energy Monitoring or other external hard-
ware should be obtained with the debug USB cable disconnected.
UG308: Thunderboard EFM8UB3 User's Guide
Debugging
silabs.com
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